Tropical Depression TWELVE

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TROPICAL DEPRESSION TWELVE DISCUSSION NUMBER 5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT THU SEP 04 2003
ALTHOUGH THE PRESSURE HAS BEEN FALLING IMPRESSIVELY TODAY...WITH THE
LATEST REPORT FROM THE RECONNAISSANCE AIRCRAFT OF 1002 MB...THE
WINDS HAVE NOT YET REACHED THE POINT THAT JUSTIFIES AN UPGRADE TO
STORM STATUS. THE PEAK WIND FROM THE AIRCRAFT IN THE CONVECTION
SOUTHEAST OF THE CENTER WAS 38 KT...OR ABOUT 30 KT WHEN ADJUSTED TO
THE SURFACE...BUT THIS AREA WAS NOT SAMPLED AFTER THE MOST RECENT
PRESSURE FALL. I EXPECT THAT THE WINDS ARE CURRENTLY INCREASING AND
TROPICAL STORM STATUS WILL BE CONFIRMED BY THE NEXT AIRCRAFT WHICH
WILL BE IN THE SYSTEM NEAR 00Z.
THE CENTER JUMPED EASTWARD INTO THE CONVECTION EARLIER TODAY...
MAKING THE INITIAL MOTION HARD TO ESTIMATE. MY BEST ESTIMATE IS
090/6. GLOBAL MODELS MAINTAIN A WEAK WEST-SOUTHWESTERLY STEERING
FLOW OVER THE GULF AND SOUTHEASTERN STATES OVER THE FIRST HALF OF
THE FORECAST PERIOD....AND CONSEQUENTLY THE OFFICIAL FORECAST CALLS
FOR A SLOW EAST-NORTHEASTWARD MOTION FOR THE NEXT TWO DAYS. AFTER
THAT...RIDGING BEHIND HURRICANE FABIAN...AND A WEAK MID-LEVEL LOW
IN THE SOUTHEASTERN STATES COULD HELP KEEP THE DEPRESSION
RELATIVELY CLOSE TO THE U.S. COAST. MODEL GUIDANCE DIVERGES AFTER
THAT...HOWEVER...WITH THE UKMET AND NOGAPS HAVING A MORE ZONAL
MID-LEVEL FLOW TAKING THE CYCLONE OUT TO SEA RELATIVELY QUICKLY.
THE OFFICIAL FORECAST LEANS MORE TO THE GFS AND GFDL SOLUTIONS WITH
A TRACK CLOSE TO THE COAST. IF THE CYCLONE TAKES A PATH
SIGNIFICANTLY LEFT OF THE OFFICIAL FORECAST TRACK...IT COULD BECOME
ABSORBED INTO A FRONTAL TROUGH BEFORE THE END OF THE FORECAST
PERIOD.
THE DEPRESSION IS STILL UNDER SOUTHWESTERLY SHEAR...ALTHOUGH THIS
APPEARS TO BE RELAXING SOMEWHAT. THIS SHEAR IS EXPECTED TO MAKE
RAPID STRENGTHENING PRIOR TO LANDFALL DIFFICULT. AFTER THE CYCLONE
ENTERS THE ATLANTIC...THE SHEAR IS EXPECTED TO INCREASE AND LIMIT
REINTENSIFICATION.
THERE IS A LARGE AREA OF RAIN ASSOCIATED WITH THE DEPRESSION TO THE
EAST OF THE CENTER...AND THESE RAINS ARE ALREADY AFFECTING PORTIONS
OF FLORIDA. REGARDLESS OF WHETHER THIS SYSTEM BECOMES A TROPICAL
STORM OR NOT...IT POSES A SIGNIFICANT RAINFALL/FLOODING THREAT.
FORECASTER FRANKLIN
FORECAST POSITIONS AND MAX WINDS
INITIAL 04/2100Z 27.8N 86.0W 30 KT
12HR VT 05/0600Z 27.9N 85.0W 35 KT
24HR VT 05/1800Z 28.3N 83.8W 40 KT
36HR VT 06/0600Z 28.8N 82.6W 45 KT...INLAND
48HR VT 06/1800Z 29.5N 81.5W 35 KT...INLAND
72HR VT 07/1800Z 31.5N 79.0W 35 KT...OVER WATER
96HR VT 08/1800Z 33.5N 76.0W 35 KT
120HR VT 09/1800Z 35.5N 72.5W 35 KT
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